Quantification and distribution of α1‐adrenoceptor subtype mRNAs in human prostate: comparison of benign hypertrophied tissue and non‐hypertrophied tissue

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Abstract
1 There are at least three α 1‐adrenoceptor subtypes, α1a, α1b and α1d, in human tissues. Using an RNase protection assay, we have now determined the amount of each subtype mRNA in human prostatic tissue, for both benign prostatic hypertrophy (BPH) and non‐BPH. In all tissue samples examined, the predominant subtype mRNA was α1a. The total abundance of α1‐adrenoceptor mRNA in BPH samples was over six times that in non‐BPH samples. This increase was mostly accounted for by α1a, which was almost nine times as abundant in BPH samples as in non‐BPH samples. The abundance of α1b was almost the same between BPH and non‐BPH samples, and the abundance of α1d in BPH samples was about three times that in non‐BPH samples. The ratio of the numbers of the subtype mRNAs, α1a:α1b:α1d, was 85:1:14 in BPH samples and 63:6:31 in non‐BPH samples. 2 In situ hybridization studies showed no significant differences in the tissue localization of α1‐adrenoceptor subtype mRNAs between BPH and non‐BPH samples, α1a and α1d were clearly detected in the interstitium of the prostate, where α1a was stained more intensely than α1d, and the positive sites were primarily smooth muscle cells. In contrast, α1b staining was very faint. 3 This increase in mRNA abundance may be directly related to the contraction of prostatic tissue that leads to obstruction of the urinary tract in BPH patients. Specifically, our data suggest that increased expression of the α1a subtype may be primarily responsible for the contraction of the prostate.